Folding formers are triangular sheet metal elements over which a web is guided. The edges of the sheet metal elements should be smooth and round since the paper web folds thereover. Further, it is desirable that the edges have air supply connections to permit application of air at a differential pressure with respect to ambient air. A typical folding former of the type to which the invention relates is shown in German Published Patent Application DE-AS No. 22 40 397. The lateral edges of the former can be constructed in the form of tubes or pipes of constant diameter, for example by welding the pipes on a sheet metal element. This construction is comparatively inexpensive in manufacture; the former, however, does not have the most desirable shape. For best guidance of paper web of the former triangle, it is desirable that the radius of curvature of the lateral edges decrease continuously towards the apex of the triangle defined by the former. Thus, the air ducts at the lateral edges should have generally conical shape, with their interior diameter decreasing towards the apex of the former. Manufacture of tubes or pipes with conical shape is very expensive.